Measurement of arterial blood gases is one of the most frequently performed tests on critically ill patients. Determination of blood gas concentrations (such as pCO2) is conducted by intermittent sampling and analysis using a bench-top analyzer. However, results are not ready until several minutes after the blood samples are taken, and these delayed data may not reflect actual patient status. Continuous blood gas determination would allow for immediate detection of changes in the status of ICU patients, of patients with acute respiratory disorders, and of patients undergoing major surgery (such as bypass surgery). To date, the lack of reliable and inexpensive miniature sensors has been a critical factor preventing wide use of continuous in-vivo gasometry. We have devised a novel approach, using the enabling technology of pH sensors based on the novel molted carbonate iridium oxide (IrOx) deposition process. This technique will allow for commercial products of miniature sensors for continuous monitoring of blood pH and pCO2 levels. In Phase I, our goal is to develop such prototype sensors and to demonstrate their feasibility. Our reserch will be focused on development of solid electrolyte membranes for blood pH and blood pCO2 sensors. Further we will investigate fesibility of silicone carbide micrifabrication technology for mass _roduction of the sensors. In Phase II, we will refine the design, optimize microfabrication process and !perform the necessary development steps towards human testing. Our ultimate aim is to develop commercial devices that will utilize this sensor, such as cannulae for open-heart surgery.